Digital broadcasting networks can be used to deliver enhanced services to users having digital broadcasting receivers. Examples of digital broadcasting networks include a Digital Video Broadcasting (DVB) network, a Digital Audio Broadcasting (DAB) network, an Advanced Television Systems Committee (ATSC) network and an Integrated Service Digital Broadcasting (ISDB) network.
It is proposed to provide Internet Protocol Datacast (IPDC) services as part of a terrestrial Digital Video Broadcasting (DVB-T) system or handheld DVB (DVB-H) system. IPDC permits data to be transmitted at high transfer rates to many users simultaneously and so can be used to stream video content and transfer data files.
It is also proposed to incorporate a DVB receiver into a conventional mobile telephone handset or personal digital assistant (PDA). This has the advantage that it allows a user to download large amounts of data quickly using IPDC, data which ordinarily would take too long and be prohibitively expensive to transfer using a conventional mobile handset and conventional public land mobile networks.
Initially, provision of DVB transmitters and implementation of IPDC is unlikely to be widespread. Therefore, service coverage is likely to be limited. Therefore, it is desirable to extend service coverage wherever possible. Furthermore, even when further transmitters are installed and IPDC becomes more widely available, it is still desirable to maximise service coverage.
Service coverage is often restricted because receivers are taken indoors. Walls and other parts of a building attenuate transmitted signals. Thus, although service coverage may be adequate outdoors, it may be insufficient indoors even though the receiver has moved just a few meters. Additionally, service coverage may be impeded by other buildings.
Extension sets are known. EP-A-1076376 describes an extension set for a DVB-T receiver in which the extension set and receiver are connected by a wired link. This has the disadvantage that it restricts mobility of the mobile terminal. WO-A-02089361 also describes an extension set for a DVB-T receiver in which the extension set re-emits a received signal. However, this has a drawback of being indiscriminate. Thus, a receiver may receive signals from a number of extension sets and the signals may interfere. DE-A-10123556 describes a mobile terminal holder in which the holder transmits a signal to the mobile telephone. However, the signal can be significantly attenuated during transmission.
The present invention seeks to ameliorate at least some these problems.